A lamp ballast is a current-limiting device used in connection with a fluorescent or other electric-discharge lamp to provide the correct circuit conditions for starting and operating the lamp. The ballast limits the current to the value for which the lamp is designed and provides the required starting voltage when the lamp is switched on. Not all lamps have the same power waveform requirements. Lamps with different waveform requirements have traditionally required the use of different lamp ballasts.
One use for lamp ballasts is in digital projectors. Digital projectors include a lamp ballast compatible with the projector lamp. Often, a lamp ballast from one projector design has a different waveform than a lamp ballast from another projector design. As a result, newly designed projectors frequently require a newly designed lamp ballast with a new waveform.
Designing a lamp ballast with a new waveform traditionally requires a large investment of time and expense. Furthermore, a newly designed lamp ballast is often used for only a few years before the projector for which it was deigned becomes obsolete. As a result, much effort is put into designing lamp ballasts that have only a short useful life.